45D-15 |
Peanut surface energy modification for improvement of whey protein coating adhesion |
S. Y. LIN and J. M. Krochta. Dept. of Food Science & Technology, Univ. of California, Davis, 1 Shields Ave., Davis, CA 95616 Whey protein films possess excellent oxygen barrier properties and thus have potential to be formed as coatings to improve the shelf life of nuts. However, adhesion of hydrophilic whey protein coatings to hydrophobic foods such as peanuts is inherently poor due to differences in the chemical nature of the two surfaces. To improve the adhesion of whey protein coating on peanuts, this research aimed at two mechanisms of adhesion, adsorption and mechanical interlocking. The objectives were to increase the surface energy of peanuts by modifying the peanut surface by surfactant solution treatment and by mechanical roughening. Peanuts were treated with aqueous lecithin solution at concentrations of 0.2, 0.4, 0.6, 0.8, and 1.0% (w/w). Surface energies of peanuts were measured and compared before and after treatment. Peanuts were also tumbled together with rock salt in a coating pan for 10, 20, 30, 40 minutes to increase the surface roughness and thus increase the surface energy of peanuts. Surface energy measurement was accomplished by applying a series of test liquids with surface energies in the range of 32 to 70 dynes/cm. Blanched, dry-roasted peanuts have a surface energy of 37 dynes/cm. Surface energy of peanuts treated with lecithin solution having a concentration higher than 0.4% was increased to above 70 dynes/cm, by adsorption of lecithin to the peanut surface. Tumbling of peanuts together with rock salt in a coating pan for 30 minutes increased the surface energy of peanuts to above 56 dynes/cm due to increased peanut surface roughness. The lecithin-modified peanut surface should allow better adsorption and therefore better adhesion by whey protein coating. Roughening of the peanuts surface should also improve adhesion by whey protein coating by increased mechanical interlocking between coating and peanut surface. Thus, the oxygen-barrier function of the coating would be maintained and greater peanut shelf-life achieved.
Session 45D, Food Packaging: General
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